Mercurial > hg
view contrib/python3-ratchet.py @ 40021:c537144fdbef
wireprotov2: support response caching
One of the things I've learned from managing VCS servers over the
years is that they are hard to scale. It is well known that some
companies have very beefy (read: very expensive) servers to power
their VCS needs. It is also known that specialized servers for
various VCS exist in order to facilitate scaling servers. (Mercurial
is in this boat.)
One of the aspects that make a VCS server hard to scale is the
high CPU load incurred by constant client clone/pull operations.
To alleviate the scaling pain associated with data retrieval
operations, I want to integrate caching into the Mercurial wire
protocol server as robustly as possible such that servers can
aggressively cache responses and defer as much server load as
possible.
This commit represents the initial implementation of a general
caching layer in wire protocol version 2.
We define a new interface and behavior for a wire protocol cacher
in repository.py. (This is probably where a reviewer should look
first to understand what is going on.)
The bulk of the added code is in wireprotov2server.py, where we
define how a command can opt in to being cached and integrate
caching into command dispatching.
From a very high-level:
* A command can declare itself as cacheable by providing a callable
that can be used to derive a cache key.
* At dispatch time, if a command is cacheable, we attempt to
construct a cacher and use it for serving the request and/or
caching the request.
* The dispatch layer handles the bulk of the business logic for
caching, making cachers mostly "dumb content stores."
* The mechanism for invalidating cached entries (one of the harder
parts about caching in general) is by varying the cache key when
state changes. As such, cachers don't need to be concerned with
cache invalidation.
Initially, we've hooked up support for caching "manifestdata" and
"filedata" commands. These are the simplest to cache, as they should
be immutable over time. Caching of commands related to changeset
data is a bit harder (because cache validation is impacted by
changes to bookmarks, phases, etc). This will be implemented later.
(Strictly speaking, censoring a file should invalidate caches. I've
added an inline TODO to track this edge case.)
To prove it works, this commit implements a test-only extension
providing in-memory caching backed by an lrucachedict. A new test
showing this extension behaving properly is added. FWIW, the
cacher is ~50 lines of code, demonstrating the relative ease with
which a cache can be added to a server.
While the test cacher is not suitable for production workloads, just
for kicks I performed a clone of just the changeset and manifest data
for the mozilla-unified repository. With a fully warmed cache (of just
the manifest data since changeset data is not cached), server-side
CPU usage dropped from ~73s to ~28s. That's pretty significant and
demonstrates the potential that response caching has on server
scalability!
Differential Revision: https://phab.mercurial-scm.org/D4773
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Wed, 26 Sep 2018 17:16:56 -0700 |
parents | 3790610c2793 |
children | 2372284d9457 |
line wrap: on
line source
# Copyright 2012 Facebook # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. """Find tests that newly pass under Python 3. The approach is simple: we maintain a whitelist of Python 3 passing tests in the repository, and periodically run all the /other/ tests and look for new passes. Any newly passing tests get automatically added to the whitelist. You probably want to run it like this: $ cd tests $ python3 ../contrib/python3-ratchet.py \ > --working-tests=../contrib/python3-whitelist """ from __future__ import print_function from __future__ import absolute_import import argparse import json import os import subprocess import sys _hgenv = dict(os.environ) _hgenv.update({ 'HGPLAIN': '1', }) _HG_FIRST_CHANGE = '9117c6561b0bd7792fa13b50d28239d51b78e51f' def _runhg(*args): return subprocess.check_output(args, env=_hgenv) def _is_hg_repo(path): return _runhg('hg', 'log', '-R', path, '-r0', '--template={node}').strip() == _HG_FIRST_CHANGE def _py3default(): if sys.version_info[0] >= 3: return sys.executable return 'python3' def main(argv=()): p = argparse.ArgumentParser() p.add_argument('--working-tests', help='List of tests that already work in Python 3.') p.add_argument('--commit-to-repo', help='If set, commit newly fixed tests to the given repo') p.add_argument('-j', default=os.sysconf(r'SC_NPROCESSORS_ONLN'), type=int, help='Number of parallel tests to run.') p.add_argument('--python3', default=_py3default(), help='python3 interpreter to use for test run') p.add_argument('--commit-user', default='python3-ratchet@mercurial-scm.org', help='Username to specify when committing to a repo.') opts = p.parse_args(argv) if opts.commit_to_repo: if not _is_hg_repo(opts.commit_to_repo): print('abort: specified repository is not the hg repository') sys.exit(1) if not opts.working_tests or not os.path.isfile(opts.working_tests): print('abort: --working-tests must exist and be a file (got %r)' % opts.working_tests) sys.exit(1) elif opts.commit_to_repo: root = _runhg('hg', 'root').strip() if not opts.working_tests.startswith(root): print('abort: if --commit-to-repo is given, ' '--working-tests must be from that repo') sys.exit(1) try: subprocess.check_call([opts.python3, '-c', 'import sys ; ' 'assert ((3, 5) <= sys.version_info < (3, 6) ' 'or sys.version_info >= (3, 6, 2))']) except subprocess.CalledProcessError: print('warning: Python 3.6.0 and 3.6.1 have ' 'a bug which breaks Mercurial') print('(see https://bugs.python.org/issue29714 for details)') sys.exit(1) rt = subprocess.Popen([opts.python3, 'run-tests.py', '-j', str(opts.j), '--blacklist', opts.working_tests, '--json']) rt.wait() with open('report.json') as f: data = f.read() report = json.loads(data.split('=', 1)[1]) newpass = set() for test, result in report.items(): if result['result'] != 'success': continue # A new passing test! Huzzah! newpass.add(test) if newpass: # We already validated the repo, so we can just dive right in # and commit. if opts.commit_to_repo: print(len(newpass), 'new passing tests on Python 3!') with open(opts.working_tests) as f: oldpass = {l for l in f.read().splitlines() if l} with open(opts.working_tests, 'w') as f: for p in sorted(oldpass | newpass): f.write('%s\n' % p) _runhg('hg', 'commit', '-R', opts.commit_to_repo, '--user', opts.commit_user, '--message', 'python3: expand list of passing tests') else: print('Newly passing tests:', '\n'.join(sorted(newpass))) sys.exit(2) if __name__ == '__main__': main(sys.argv[1:])